1. Field of the Invention
The present invention relates to a radiation detection device; and, in particular, to a radiation detection device having a light-receiving portion with a large area, which is used for medical x-raying and the like.
2.Related Background Art
While X-ray sensitive films have conventionally been used for medical and industrial X-raying, radiation imaging systems using a radiation detection device are becoming pervasive due to their convenience and the storability of their photographed results. Such a radiation imaging system uses a radiation detection device having a plurality of pixels so as to acquire, as an electric signal, two-dimensional image data formed by a radiation, and processes thus obtained with a signal processing unit, so as to display it on a monitor. A typical radiation detection device is configured such that a scintillator is disposed on one- or two-dimensionally arranged photodetectors so as to convert the incident radiation into light, which is then detected.
Cesium Iodide (CSI), a typical scintillator material, is a hygroscopic material which dissolves by absorbing vapor (moisture) in the air. As a result, characteristics of the scintillator, such as resolution in particular, have disadvantageously deteriorated.
One radiation detection device having a structure for protecting the scintillator against moisture is the technique disclosed in Japanese Patent Application Laid-Open No. 5-196742. In this technique, a water-impermeable moisture-proof barrier is formed on the upper side of the scintillator layer, thereby protecting the scintillator against moisture.